Method for grinding trochoidal and circular bearing races

Abstract

A method for grinding epitrochoidal, hypotrochoidal, and circular bearing races in one set-up without moving the part and insuring near perfect concentricity between all of the bearing races. A machine blank is mounted on an upper rotary table that is in turn mounted on a lower rotary table. The upper table is driven both by the lower table and by an independent servomotor. The net speed of the upper table is the difference between the two driving speeds of the tables. The axis of rotation of the upper table can be offset from the axis of rotation of the lower table. The tables are rotated in opposite directions while a grinding wheel is moved laterally into contact with the surface of a rough-machined part to form the trochoidal surface. The characteristics are determined by the offset, the diameter of any rollers that are to be positioned between the trochoidal surfaces in the speed change device, and the relative speeds of the two tables. After the trochoidal surface or surfaces are completed, the lower table is stopped in its home position and the upper table is driven to grind the circular bearing race or races. Three independently-driven grinding spindles are laterally adjustable with respect to the tables.

What is claimed is: 
     
       1. The method of forming a trochoidal surface on a blank for use in a speed change device comprising the steps of providing a first rotary table,   mounting a second rotary table on said first table so that it is free to rotate relative to said first table,   displacing the axis of rotation of said second table from said the axis of rotation of said first table by a predetermined distance,   securing said blank to said second table,   driving said second rotary table in a direction opposite from said first table,   providing a grinding wheel, and   rotating said grinding wheel while in contact with said blank and during the rotation of both of said tables.   
     
     
       2. The method as claimed in claim 1 wherein said part is an eccentrically mounted rotor having an outer epitrochoidal surface for use in a speed change device in which the rotor is positioned within a hypotrochoidal bearing race separated by a plurality of spaced circumferentially positioned rollers, and   the speed of said second table is equal to the speed of said first table minus 1/(N-1) where N is equal to the number of rollers to be positioned between said epitrochoidal surface and said hypotrochoidal bearing race.   
     
     
       3. The method as claimed in claim 2 wherein the diameter of said grinding wheel is approximately equal to the diameter of one of said rollers.   
     
     
       4. The method as claimed in claim 1 wherein said part includes a hypotrochoidal bearing race for use in a speed change device in which the said bearing race surrounds an eccentrically mounted rotor having an outer epitrochoidal surface and separated by a plurality of spaced circumferentially positioned rollers, and   the speed of said second table is such that for each turn of the first table, the second table will rotate in the opposite direction one turn plus 1/(N+1) turn, where N is equal to the number of rollers to be positioned between said part and said epitrochoidal surface.